Aircraft maintenance mainly consists of curative actions aiming at replacing or repairing failing equipments of the aircraft or equipments currently being degraded, by planned inspections, generally periodic, and by preventive actions such as the replacement of equipment having a finite lifetime. The curative actions rely particularly on the knowledge of the airplane state which is in particular obtained by the aircrew reports, the onboard diagnostic systems and the inspections made during the planned checks.
Commonly, the maintenance activity is organised into “line maintenance” and “hangar maintenance”. The hangar maintenance is performed during pre-programmed checks. Such maintenance operations are often made at the main operating base of the airline operating the aircraft. The line maintenance is performed between two flights, at the place where the aircraft is. The main object of the line maintenance is the urgent curative actions whereas the hangar maintenance enables planned tasks as well as deferred curative actions to be performed.
However, these maintenance policies are not always optimal. In particular, by deferring these curative actions to the successive check, the line maintenance increases the risk that a further degradation causes a flight departure delay or cancellation or other disturbances.